摘要
We present a facile and scalable method to prepare water-dispersed polyvinylpyrrolidone-capped graphene (PVP-graphene) nanoplatelets from an ordinary graphite powder. The 3 D hydrophobic graphite powder was exfoliated into 2 D hydrophilic PVP-graphene nanoplatelets by inducing intercalation through the PVP chains and through high-powered sonication. The nanoplatelets were characterized by using XRD, field-emission scanning electron microscopy, TEM, Raman spectroscopy, and X-ray photoelectron spectroscopy, and they were found to be nonoxidative and to have dimensions of a few hundred nanometers. The suitability of PVP-graphene as a catalyst for a CoII/III redox couple was evaluated by coating the prepared PVP-graphene nanoplatelets on fluorine-doped tin oxide glass through a unique two-step dipping method. The coated nanoplatelets were examined by using electrochemical impedance spectroscopy, UV/Vis spectroscopy, and current–voltage curve analysis, and it was observed that PVP-graphene exhibited a high catalytic effect because the charge transfer resistance from CoIII to CoII was as low as 1.17 Ω cm2. A porphyrin-sensitized solar cell with this counter electrode and an efficiency of 8.95 % was demonstrated.